Experimental investigation of thermophysical properties of Al2O3–water nanofluid: Role of surfactants

Abstract

Nanofluids are colloidal suspension of nanoparticles that have attracted much attention due to their enhanced heat transfer characteristics. Stability of the nanofluid is important for industrial applications. Although several researchers studied thermophysical properties of nanofluids, the literature is replete with contradictory results. The aim of the present work is to experimentally investigate the stability and properties of Al2O3-water nanofluid and the effect of surfactant on those; the effects of both temperature (20–60°C) and solid volume fractions (0.1–2.0%) of nanofluids are also analyzed. Stability of the nanoparticle suspensions is investigated with different surfactants, when sodium dodecylbenzenesulfonate (SDBS) is found to offer the best stabilization. TEM images show presence of rod-like particle of 20–70nm size. DLS measurements indicate that the presence of SDBS surfactant reduces particle clustering and polydispersity index of the suspension. Rheological measurements show that viscosity of Al2O3-water based nanofluids increases with solid volume fraction (φ=0.1–1.0%) and decreases with temperature, while the thermal conductivity increases with the increase of both solid volume fraction (0.1–2.0%) and temperature. The observed values of thermal conductivity and viscosity are compared with different established models. Finally, a sensitivity analysis is performed, which reveals that, for a given temperature, the sensitivity of thermal conductivity increases with the particle loading. The results provide comprehensive thermophysical property database of water-based Al2O3 nanofluids for different engineering applications.